It is known to provide a seat restraint system such as a seat belt in a vehicle to restrain an occupant in a seat of the vehicle. In some vehicles, the seat restraint system may be a lap belt, a shoulder belt, or both. Typically, the lap belt and shoulder belt are connected together at one end. The seat restraint system includes a latch plate at the connected end. The seat restraint system also includes a buckle connected at one end by webbing or the like to vehicle structure. The buckle receives the latch plate to be buckled together. When the buckle and latch plate are buckled together, the seat restraint system restrains movement of the occupant to help protect the occupant during a collision.
Smart inflatable restraint systems need to know what is occupying a seat of the vehicle. Decisions on deployment of inflatable restraints depend on information supplied by sensors in the seat in determining weight of an object in the seat. When a child seat is placed in the seat and cinched down, the sensors may read a large mass instead of a child seat. With this condition, there will be high tension in the seat restraint system. Comfort studies have shown that no human occupant would wear their seat restraint that tight. With this information on seat restraint tension, the inflatable restraint system can decide on deployment of the inflatable restraints.
Conventional belt tension sensors typically include compression springs for sensing capability. However, these compression springs do not provide adequate sensing capability at low tension levels. In addition, these tension sensors may exhibit rattle noise and have a relatively large package size. Further, these tension sensors may be subject to environmental contamination. Additionally, these tension sensors have an inability to be packaged on either an inboard side or outboard side of a passenger seat of the vehicle. Also, these tension sensors are not compatible with buckle pretensioners.
Therefore, it is desirable to provide an assembly for sensing tension in a seat restraint system of a vehicle. It is also desirable to provide an assembly for sensing tension in a seat restraint system in a vehicle that allows a control module to decide on deployment of the inflatable restraints. It is further desirable to provide an assembly for sensing tension in a seat restraint system in a vehicle that provides an indication of low-tension forces in the seat restraint system. It is still further desirable to provide an assembly for sensing tension in a seat restraint system having a smaller package size. Therefore, there is a need in the art to provide a tension sensing assembly that meets these desires.